It's been a while for me, but IIRC it's pretty effortless. The FE2 is capable of TTL, one of the reasons it was the last film camera to leave my kit. I did check the SB-20 features and it is a TTL strobe so I think you can just put the SB-20 on the hot shoe, set to TTL.

For short distances, I typically set my TTL daylight fill to -1.5EV. However, for the SB-20, the low-res photos I found were not sufficient for me to locate a exposure compensation setting on the unit itself, so you might have to fool it by setting one EV higher ISO setting on the strobe.

In my film days, I kept a careful log of exposures and tried different settings at the beginning of each roll of film and then evaluated them over time.

Roger
It's still, ISO, aperture and shutter-speed, right?